This was the key to the fight. I tried this quest at level 29 several times and died miserably. Went away and got 30, came back to face the same result with both Vette and Quinn. Then I read this thread and started each wave behind the barrels, only coming out after the soldiers had built up decent aggro. The fight was a piece of cake. In the first wave, I let the soldiers do almost all the work. In the second, I let the main quest guy kill one of the tougher dudes and killed the other myself. In the third wave, I let the quest dude start the fight and then jumped in. I hardly drew aggro at all. Using those barrels made a night and day difference.